A more practical approach is
to first identify the different column density regimes in the cloud and
then to sample each regime by choosing a number of cloud positions at random.
This sampling approach is an instance
of the “stratified random sampling”
technique often used in surveys [1]}, and whose name derives
from the word “strata” used to denote the
different subpopulations of the sample, which in our case correspond to the
column density regimes of the cloud.
